(also oxyquinoline, oxine); light yellow crystals with a melting point of 75°–76°C. 8-hydroxy-quinoline has the following structural formula:

Organic solvents, alkalis, and acids are good solvents for 8-hydroxyquinoline, but the compound is only slightly soluble in water. 8-hydroxyquinoline forms crystalline chelates, such as Mg(C₉H₆ON)₂ and Al (C₉H₆ON)₃; these are only slightly soluble in aqueous solutions, including acetic acid and ammonia. The capacity of 8-hydroxyquinoline to form chelates is used to detect and isolate a number of metals, including aluminum, zinc, cadmium, and magnesium. Some 8-hydroxyquinoline derivatives are used as fungicides, for example, the copper salt Cu(C₉H₆ON)₂. Others, for example, Quinosol, Entero-Septol, and Yatren, are used as surface antiseptics or to kill amoebas.